Grinding wheel



May 12, 1942. E. VAN DER PYL GRINDING WHEEL Filed Sept. 11, 1939 I Patented May 12, 1942 GRINDING WHEEL Edward Vander Pyl, Holden, Mass., assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Application September 11, 1939, Serial N... 294,210 i 1 Claim.

The invention relates to grinding wheels and particularly diamond grinding wheels.

One object of the invention is to provide a facile method forattaching a diamond abrasive rim to a solid metal back. Another object of the invention is to mak a grinding wheel which is metal throughout," that is consists of a metal back and an abrasive part which has abrasive grains bonded with metal without the necessity of pressing and sintering the backing but instead thereof using a cast or a machined metal backing. Another object of the invention is to form a firm union between a pressed and sintered metal bonded abrasive rim and a machined or cast metal backing. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and ,ord'er of each of said steps to one or more of the others thereof, all as will be illustratively described herein and the scope of the application of which will be indicated in the following claim.

In the accompanying drawing showing one of many possible embodiments of the mechanical features of this invention,

Figure 1 is a cross sectional view through mold in which is located the cast or machined backing and a mixture of abraisve and metal powders about to be pressed.

Figure 2 is a view the same as Figure 1 but showing the mold closed.

Figure 3 is an enlarged cross sectional view of that portion of the mold which contains the metal and abrasive powders prior to pressing.

Figure 4 is a view the same as Figure 3 but after the mold has been closed.

Figure 5 is a plan view of the backing, on the same scale as Figures 1 and 2, before it is placed in the mold.

Referring first to Figure 1 I provide an outer mold ring I and an inner mold block II. In also provide a pressing ring I2. These parts the shapes of which are sufficiently indicated in Figures 1 and 2 constitute the mold. They may be located upon the platen I 3 of a suitable hydraulic press and a top plunger, not shown, is used to close the mold with any desired pressure.

Located in the ring In and supporting the block II is a metal backing I that is going to form part of the finished article. This may be made in any suitable way but one of the objects of the invention is to dispense with the steps of pressing and sintering the metal backing or any part thereof. That is to say it may be more convenient or economical to use a preformed backing I 5.. Such a backing can be castffor example it can be made of cast? steel. However I do not wish to limit myself to the use of castings since the backing might be machined from a blank and furthermore the backing might be formed bya forging process. Metals other than ferrous metals can be used such as copper, bronze, brass, aluminum. vIt is preferred, however, that the metal usedas a backing hav sufficient ductility or malleability so that it can be slightly deformed. Most of the ferrous metals have sufflcient ductility or malleability excepting that gray cast iron is preferably not used. On the other hand wrought iron or malleable iron are readily usable carrying out my invention.

' Referring now especially to Figures3 and 5 I form undercut grooves I6 in the top surface of the backing I5 which in the illustrative embodiment has the form of a dish. This leaves annular ridges H which are preferably slightly undercut as shown. The annular ridges I! have a dove-tailed shape in cross section. The grooves I6 may be cut with any suitable turning tool and in fact the grooving of the backing can well be effected in a lathe.

After placing the backing I5 inside the ring Ill and placing the block I I upon the backing I5, as shown, I fill the annular space between them to a certain depth with an abrasive metal mixture in comminuted form. Preferably I use a mixture of diamond particles and copper and tin in powdered form as set forth in my Reissue Letters Patent No. 21,165. I prefer to use about 20% of tin and of copper by weight and then form a total mixture of the powdered metals with diamond abrasive. I may provide diamonds to the extent of about 25% of the total mixture by volume but the proportion of abrasive can be widely varied. Using 50% of diamonds, or even more by volume, there is enough metal bond to make a. strong article, while down to even 5% of diamonds will provide abrasive enough to do some cutting. Excellent results in actual practice, however, are achieved using 25% of diamonds by volume.

The metals should be finely divided but commercial powders are readily usable. The practical size of the diamonds will vary according to the type of finish that is desired, but I find excellent results in practice by the use of anywhere between grit size up to 300 and even 400 grit size. Abrasive grit sizes are referred to which are measured by screen having that many meshes to the linear inch given as the measure of the grit size.

I may also use other powdered metals and the invention is not to be deemed limited in any way to the particular metals specified. For exam- Dle I may use any of the other mixtures specified in my Reissue Patent No. 21,165, namely copper and any of nickel, aluminum, manganese, or beryllium. ,Bonds made in accordance with my reissue Letters Patent are characterized by friableness which has been found to be an excellent quality for metal bonds for diamond abrasive articles. In patent to Milllgan No, 2,077,366 there are disclosed alloys of copper and aluminum, zinc andaluminum, silicon and nickel, silicon and iron, silicon and copper, and silicon and chromium and I may use any such alloys in powdered form or introduce the separate metals in powdered form into the mold. In my own prior Patent No. 2,077,345 I have disclosed a bond for diamond abrasive specifically consisting of 40 parts of aluminum and 60 parts of silicon and I may use this mixture.

With regard to whether to make an alloy of the two or more metals used and then powder the alloy or to use a mixture of powders each one being a powder of an elementary metal, practical considerations make the latter course preferable. The powders will sinter together forming an alloy readily enough if the melting points are not too far apart and it is easier to procure the elementary metal in powdered form. I may use electrolytic iron as disclosed in patent to Gauthier No. 1,625,463 or I may mix electrolytic iron with suitable proportions of carbon or any other ingredient to change the characteristics of the iron. n the other hand it is practical also to use finely divided steel or cast iron of a particular grade desired.

Having charged the mold with the desired mixture of diamond abrasive and powdered metal bond I place the pressure ring I! in position as shown in Figure 1 and then close the mold. This is done by bringing the upper platen of a hydraulic press down upon the ring l2 and forcing the top of it level with the ring l2 and the block II. The effect of so doing is shown in Figures 2 and 4. The pressure acting through the partially plastic material 2| deforms the ridges l7, causing the area of their top surfaces to increase, increasing the overhang of the dovetails, and at the same time reducing them in height. At the same time, the pressure consolidates the loose mixture 2| into a rigid article which is locked to the backing l5.

After this operation I strip the now formed grinding wheel consisting of the backing I5 and the abrasive portion from the mold. This may be done in the usual manner and I provide tapped holes 22 in the block H for the insertion of eye bolts to assist in the stripping. The abrasive portion is consolidated but greater strength can be imparted to it by a sintering operation. I now sinter the abrasive portion by placing the entire article in a furnace, preferably with hydrogen flame curtains, and raise the oven to a temperature slightly below the melting point of the metal which melts at the lowest temperature. In the case of the copper tin mixture mentioned first I may satisfactorily sinter at a temperature of 700 C. This sintering forms a homogeneous mass from the previously compressed powders and gives the metal bond the character of a true alloy.

It will be noted that the pressing operation greatly reduces the height of the ridges l1. Thereby but a small amount of total diamonds are embedded in the grooves l6. At the same .time complementary dove-tails are formed in the grooves IE to interlock with the dove-tailed annular ridges I! to form a firmunion between the abrasive portion and the backing [5. The article can be used for grinding right down to the tops of the ridges l1 and is not useless for grinding even after that, for, if a traverse is used, the abrasive dove-tailed annular ridges 22 will abrade and dove-tailed annular ridges I! will readily wear down with the gradual wear of the abrasive. If desired the sintering may be done at the same time as the pressing and in such a case the press platens are heated and flames may be directed against the outer mold rim In.

It will thus be seen that there has been provided by this invention a methodand an article in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth, or shown in the accompanying drawing,

is to be interpreted as illustrative and not in a,

limiting sense.

I claim:

Method of making a composite abrasive article which comprises forming annular dovetailed grooves with intervening annular dovetailed ridges in a ductile metal backing; placing the backing in a mold; filling the mold next to the grooves with a mixture of comminuted abrasive and comminuted metal; pressing the said mixture with a pressure sufiicient to deform the ridges, causing the area of their top surfaces to increase, increasing the overhang of the dovetails, reducing them in height, thereby interlocking the pressed mixture with the backing; and then sintering the comminuted metal.

EDWARD VAN DER PYL. 

